This invention is an improvement of the prior arts of the U.S. patent applications, namely U.S. Ser. No. 08/439,509, filed on: May 11, 1995; and U.S. Ser. No. 08/600,070, filed on: Feb. 12, 1996, which were also invented by the same inventors of this invention.
However, the prior arts of the earlier U.S. patent applications have the following drawbacks:
1. Whenever folding the umbrella rib assembly from an opening state to approximate the upper notch 3 and lower runner 4, it still requires a manual operation to bias the flat-side rib means 2a towards the extremity rib means 2 in order to minimize the folding volume of the rib assembly and the umbrella cloth 5, thereby causing inconvenience for the umbrella user.
2. Either the upper slim plate 31 or the lower slim plate 41 of U.S. Ser. No. 08/439,509 is slimly elongated to form each pair of pivoting means 33, 43 disposed on two opposite end portions of each slim plate 31, 41, thereby weakening the strength and easily breaking the slim parts when subjected to tension force of an opening umbrella. The gradational structure of U.S. Ser. No. 08/600,070 has thickened the upper notch and lower runner for enhancing the strength, still requiring skillful work for assembling the rib means on the "two-story" upper notch or lower runner.
3. Each pivoting means 33, 43 is generally formed as a semicircular shape to still occupy a big volume of the folded umbrella, thereby influencing a miniaturization of the pocketable umbrella.
The present inventors have found the drawbacks of the prior arts and invented the present pocketable folding umbrella.